1. Field of the Invention
The present invention relates to a novel ferrocene derivative and, more in detail, an optically active ferrocene derivative as a useful catalyst for asymmetric synthesis. Further, the present invention relates to an optically active haloferrocene and ferrocene derivative.
2. Description of Prior Art
A catalyst is often used for an asymmetric synthesis method which is one of processes for preparation of an optically active substance. Examples of well known catalysts include ephedrine and prolinol derivatives which are derived from natural sources.
Derivatives from natural sources, however, have specificity to a substrate and as a result, some substrates exhibit good enantioselectivity but the other substrates do not. Therefore, these derivatives from natural sources can not be applied to or are not suitable to many reactions.
In these circumstances, some improvement in catalysts for asymmetric synthesis derived from natural sources were attempted in order to reduce the above-mentioned specificity to a substrate and improve properties such as reaction efficiency. However, in some cases, it is not easy to change a substituent on an asymmetric carbon in the catalyst and it is impossible to obtain a catalyst with desirable properties.
Ferrocenylphosphine, one of known optically active ferrocene derivatives, is used as a chiral ligand to transition metals such as palladium and rhodium. Transition metals with ferrocenylphosphine as the ligand are used as catalysts for asymmetric synthesis. (See T. Hayashi et al., Bull. Chem. Soc. Jpn., Vol.53, 1138 (1980); Tetrahedron Lett., 1979, 2155; J. Org. Chem., Vol. 53, 113 (1988).) However, this catalyst can be applied only to reactions in which transition metals such as palladium and rhodium work as a catalyst, and is not applicable to a wide range of reaction.
Further, it is known that catalysts using metals with Lewis acidity such as zinc, boron, aluminum, titanium, cerium and nickel exhibit good enantioselectivity in asymmetric induction. However, no catalyst consisting of a metal with Lewis acidity to which ferrocenylphosphine is coordinated has afforded high enantioselectivity.
A provision of an optically active ferrocene derivative coordinating to a metal with Lewis acidity and exhibiting good enantioselectivity is desired.
Furthermore, aside from a metal coordination catalyst, a polymer comprising an optically active ferrocene derivative is also aspired to be provided. The polymer comprising an optically active ferrocene derivative will be used as a catalyst for heterogeneous asymmetric synthesis and a gel for an optical resolution.
An object of the present invention is to provide a novel catalyst for asymmetric synthesis which can be used instead of the above-mentioned compounds derived from natural sources.
A further object of the present invention is to provide a catalyst for asymmetric synthesis of which substituents on the asymmetric carbon are easily exchangeable.
An another object of the present invention is to provide an optically active ferrocene derivative which can be a ligand to a metal with Lewis acidity.
A further object of the present invention is to provide an optically active ferrocene derivative usable as a starting material of an optically active polymer.